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The present invention relates in general to implantable devices for providing medically required treatment regimens over a period of time, and in particular to an implantable bioartificial active secretion system comprising live secretory cells providing a physiologically-required secretion to a living-being host patient in response to specific respective needs of the patient as determined by the live secretory cells in response to physiological make-up of host tissue fluid in contact with the secretory cells.
Natural production of numerous agents, metabolites, enzymes, and other secretions occur within a living being host as physiological events take place. One such event is the metabolism of carbohydrates which is controlled mainly by insulin which is produced by beta cells of the islets of Langerhans within the pancreas. In addition to its principal role in carbohydrate metabolism, insulin also significantly affects lipid, protein, and mineral metabolism in addition to the metabolism of carbohydrates prior to their ultimate break-down to glucose. When efficient insulin production by the pancreas is inhibited or terminated and therefore insufficient, as occurs substantially in Type I diabetes, for example, where immune cells of the host infiltrate the islets of Langerhans and eventually destroy the beta cells by T-cell-mediated mechanisms, insulin from another source must be provided or the affected individual will suffer from many severe consequences of diabetes mellitus.
Prior-art approaches for providing insulin to maintain proper plasma glucose concentrations are numerous. One of the most commonly employed is the injection of insulin into the patient a plurality of times daily in response to plasma-glucose monitoring. Subcutaneous injection is a usual insulin introduction route, but is flawed and/or dis-favored for several reasons. In particular, injection administration is limited because there is no direct feedback between blood glucose level and the dosage of insulin. In addition, there is poor patient acceptance, significant absorption variability among patients, potential overdosing resulting in hyperinsulinemia/hypoglycemia, potential underdosing resulting in hypoinsulinemia/hyperglycemia, formation of anti-insulin antibodies, hypersensitivity reactions due to insulin formulations, and other untoward occurrences. Relatively new jet injector devices, as opposed to traditional syringes, do not appreciably avoid syringe-injection limitations as noted above. Orally administered insulin finds poor effectiveness because of the vast variability found in digestive processes and digestion states among patients.
Another prior art approach for providing insulin to patients is the provision of wearable or implantable insulin pumps which are pre-programmed and pre-loaded with insulin, therefore there is no direct feedback of optimal dosage. Unfortunately, however, these pumps can cause both mechanical and physiological problems for the patient. With respect to the former problem, these pumps can experience catheter blockage, infection, skin inflammation, erosion, local fluid accumulation, dislocation due to patient physical activity, and required regular refills of insulin usually at monthly or bimonthly intervals. With respect to the latter problem, presently available insulin pumps do not have reliable glucose sensors and therefore are unable to precisely dispense a needed insulin quantity for proper plasma-glucose level maintenance.
Yet another prior art approach for treating insulin deficiency is the transplantation of pancreatic beta cells to the pancreas, liver, muscles, or peritoneal cavity of the patient, or the transplantation of an entire donor-pancreas as a replacement. Such an approach, however, many times is not practical because of recipient immune-rejection, limited availability of donor organs, and other restraints on patient acceptance.
In view of the above inability of prior art approaches to artificially provide a natural imitation of a physiological secretion, it is apparent that a highly important need is present first for sensing an in vivo need for a secretory product, and second for fulfilling that need by providing an appropriate quantity of secretory product. Accordingly, a primary object of the present invention is to provide an implantable bioartificial active secretion system for providing, in vivo, a physiological secretion necessary for functionality of a physiologic activity dependent upon that secretion.
Another object of the present invention is to provide an implantable bioartificial active secretion system wherein physiologically active, autonomously functioning, live secretory cells for producing the physiological secretion are protected from immune destruction by the host while sensing and responding to functional need.
Still another object of the present invention is to provide an implantable bioartificial active secretion system wherein tissue fluid of the host is introduced to the live secretory cells for cell-secretion uptake and subsequent delivery for distribution within the host.
These and other objects of the present invention will become apparent throughout the description thereof that now follows.
The present invention is an implantable bioartificial active secretion system for providing a physiological secretion necessary for functionality of a physiologic activity of a living-being host. The system first includes a housing having an inlet with an external opening thereto and an outlet with an external opening therefrom. This housing is implantable at least partially within the host such that the inlet and outlet openings are positionable in fluidic communication with tissue fluid of the host and the tissue fluid can be received into the housing and thereafter dispensed from the housing. A chamber is disposed within the housing between the inlet and outlet and in communication therewith, and contains a plurality of physiologically active, autonomously functioning, live secretory cells for producing the physiological secretion. Also disposed within the housing is a periodically-operating pump apparatus for drawing initial tissue fluid through the inlet from the host for contact with the physiologically active cells within the chamber for pick up and regulation of the physiological secretion, and for dispensing resulting tissue fluid bearing the physiological secretion through the outlet and into the host. Finally, inlet and outlet filter systems in operational communication with the external openings of the inlet and outlet have openings therethrough sized for prohibiting passage of immune system cells, immunoglobulins, and complement system components of the host.
The tissue fluid drawn to be in contact with the live secretory cells must generally reflect host requirements for the particular physiological secretion. Thus, in treating diabetes for example, peritoneal fluid is drawn since it is known that peritoneal fluid reflects blood glucose levels, whereby peritoneal fluid contacts secretory cells that are pancreatic beta cells which produce insulin for peritoneal-fluid uptake and return for routing to regulate such glucose levels. The secretory cells preferably are encapsulated with a permeable medium through which cellular nutrient as well as cellular metabolic waste can pass and likewise through which the physiological secretion can pass, but not through which immune system cells can pass on the off-chance that such cells passed through the inlet filter. Encapsulation increases the loading density of the cells and their surface interaction with the fluid. Depending upon the specific application, secretory-cell life span many times can be up to about two years, after which time replacement cells are introduced.
The pump apparatus preferably includes a plurality of sequentially disposed, peristaltic-like activated and deactivated, elasticized pump tubes for peristaltic-like moving therewithin the initial tissue fluid and the tissue fluid bearing the physiological secretion through the housing. Simultaneously, the preferred arrangement of the plurality of secretory cells is such that sub-pluralities thereof are disposed on a tray, a plurality of trays are situated into a column, and a plurality of columns are horizontally spaced from each other with respective inter-column spaces there between wherein pump tubes are situated. Peristaltic-like pumping can be accomplished electromagnetically by a programmed controller disposed with the housing and thus implanted, or by a programmed controller situated outside the patient and in proximity to the implanted housing. In either configuration, power is intermittently applied to replicate peristaltic movement of tissue fluid through the pump tubes and thus in moving contact with the live secretory cells situated within the housing. The tissue fluid must reflect whether a need is present for the particular secretion provided by the secretory cells (e.g., glucose level for insulin-secreting cells), whereby the secretory cells will naturally respond to the conveyed need and automatically produce a quantity of secretion specific to this need as sensed by the secretory cells. This secretion is picked up by the tissue fluid as it contacts the secretory cells, and thereafter is delivered within the host. Finally, when the tissue fluid indicates less need for the secretion (e.g., the required activity of the secretion has been completed for the time being), such reduced need is sensed by the secretory cells as the tissue fluid continues in contact therewith, and the secretory activity naturally ceases.
As is apparent, the implantable bioartificial active secretion system here defined significantly replicates natural metabolic function by employing live secretory cells as both sensor and provider of physiologic balance. Such live-cell employment eliminates external guess work with respect to quantity and timing of secretion-product injection or other type introduction since actual cells make a natural determination of need followed by a natural production and natural release of an exactly-necessary quantity of the secretory product.